The present invention relates to an output device which creates combined image data of a second aspect ratio by adding bands to image data of a first aspect ratio, and more particularly relates to such an output device which is connected to a display device which processes this combined image data and displays the resulting image upon a screen.
In recent years, increase of the width of the screen display of a television, a PC, or the like has progressed rapidly, and wide displays which have screens of 16:9 aspect ratio are being sold in very large numbers in the market. And output devices such as CATV receivers and DVD players and the like which are compatible with such wide displays are also being sold in very large numbers.
Here, a DVD player will be explained as a representative of such output devices. When the image data recorded upon a DVD is at an aspect ratio of 16:9, such a DVD player outputs the image data as a wide display, just as it is. Due to this, the image is displayed as a wide display at the aspect ratio of 16:9. On the other hand, if image data at the aspect ratio of 4:3 is recorded upon a DVD, the DVD player outputs a wide display by creating a combined image at the aspect ratio of 16:9, in which black colored mask bands are added to the left and right sides of an image at the aspect ratio of 4:3. As a result, a combined image at the aspect ratio of 16:9 is displayed as a wide display. In this manner, in recent years, the number of cases has been steadily increasing in which the user views a combined image at the aspect ratio of 16:9, even though the image data is recorded upon a DVD at the aspect ratio of 4:3.
It should be understood that inventions of display devices which display combined images of the above described type are disclosed in Japanese Laid-Open Patent Publication 2003-219320 and Japanese Laid-Open Patent Publication 2005-236707.
However, with a display device such as a plasma display panel (PDP) or the like, in a similar manner to the case with a CRT or the like, due to the relationship between the usage of the phosphor and its light emitting characteristics, so called “burning” may be caused upon the screen of the display device. Burning appears more and more prominently, if the same screen is displayed for a long time period, in proportion to time period that such display is performed. Accordingly, if a combined image is displayed in wide display at an aspect ratio of 16:9 for a long period of time, then the portions where the mask bands appear sometimes undergo burning, which is undesirable. As a result the problem occurs that, when an image of aspect ratio 16:9 is displayed in wide display, the portions where these mask bands were located stand out prominently due to the differences in their luminance levels.
The object of the present invention is to provide an output device with which, by adjusting the signal for the combined image which is outputted to the display device, it is possible to prevent burning of the portions where the mask bands are located.